The easiest way to reproduce is to create a telnet check that executes: echo -n '$ '.

With this item, server dies immediately:

22109:20100401:122531.335 In get_value() key:'telnet.run[uname]'
22109:20100401:122531.335 In telnet_run()
22109:20100401:122531.339 In telnet_login()
...
22109:20100401:122532.263 End of telnet_login():SUCCEED
22109:20100401:122532.263 In telnet_execute()
22109:20100401:122532.263 In telnet_read()
22109:20100401:122532.363 End of telnet_read():0
22109:20100401:122532.363 telnet_execute() command output:'$ '
22102:20100401:122532.363 One child process died (PID:22109). Exiting ...

Other related issues were also discovered, like telnet check going into an infinite loop.